The present invention relates to a medium-carrying hose, preferably for pressure medium and for use in e.g. engine compartments, the wall of the hose comprising at least one wall portion which is connected with at least one expansion portion to form a continuous hose casing. The circumference of the hose is variable between a minimum value, when the expansion portion is unexpanded, and a maximum value, when the expansion portion is maximally expanded.
The invention also relates to a method for manufacturing such a hose.
Hoses of the type that is used in engine compartments are subjected to various effects of the surroundings. For instance, they can be subjected to pressure, from inside or from outside, or to relatively powerful vibrations as the engine is running. The space for hoses in motor compartments and the like is usually very limited. For an engine unit to be compact in terms of space, it is often necessary that the hoses be preformed and bent in given directions to fit between the other components of the engine. However there is one problem since the hose, when pressurised, tends to move or bulge in the engine compartment. The hose may then abut against other parts of the engine body, which for instance because of their temperature may damage the hose. This situation may also arise if the hose vibrates in the operation of the engine. Both pressurising and vibration besides cause a strain to the attachment of the hose in the engine unit.
There are today a plurality of hoses which have some kind of bellows structure at their ends, thereby reducing the vibrations in the attachment of the hose. However, such bellow structures do not affect the motion of the various parts of the hose, which are still essentially free and can abut against neighbouring objects.
Such a hose is disclosed in e.g. EP 0 791 775, where flexible portions at the ends of the hose are combined with a rigid hose portion in the middle of the hose. Vibrations are absorbed in the longitudinal direction of the hose at the hose ends, but otherwise the hose is allowed to move freely.
According to the invention the above problems are solved by a hose of the type mentioned by way of introduction, the expansion portion of the tube extending in the transverse and the longitudinal direction of the hose, the wall portions being displaced relative to each other in the transverse as well as the longitudinal direction of the hose as the circumference increases and the expansion portion expands.
By the expansion portion extending in the transverse and the longitudinal direction of the hose, the wall portions will be displaced in the transverse as well as the longitudinal direction when, for instance, pressurizing the hose. The direction of motion of the portions during pressurising can thus be controlled, so that there is no risk of the hose touching other components in, for example, an engine unit. The wall portion has a substantially constant diameter and the expansion portions have a substantially smaller diameter than the wall. The expansion portion can extend first in one then in other direction, or diagonally across the transverse and the longitudinal direction of the hose. Also vibrations will be efficiently damped in a desirable manner when the vibrating motion of the wall portion is absorbed by the expansion portion. This means that the wall portion, and thus the hose, can be controlled in a desirable manner also in case of vibrations.
The wall and expansion portions may, if desirable, be differently formed in different parts along the hose in order to control, during expansion or vibration of the hose, the direction of motion of the different parts in a desirable manner. The relationships of the wall and expansion portions can also differ in different parts along the hose.
In such a hose, which is preformed to have a certain extent in the longitudinal direction, as is often the case of hoses intended for engine compartments, the design of, and the relationships of, the wall and expansion portions in the hose casing in each part of the hose is preferably adapted to the preform of the hose in the respective parts. One and the same preformed hose can thus advantageously be provided with differently formed expansion and wall portions.
Preferably the expansion portion may consist of a groove in the hose casing when this is in an unexpanded state. Such a groove is relatively easy to form by means of a design in which the expansion portion is formed in unity with the wall portion. The expansion of the groove can besides be controlled with the aid of the shape of its cross-section.
Preferably the groove is helically turned seen in the longitudinal direction of the hose. The helical shape means directly that the expansion portion is oriented both in the transverse and in the longitudinal direction of the hose. Pressure and shocks in both directions are therefore efficiently absorbed by the hose.
The number of turns of the helical groove per unit of length of the hose may be varied to control the hose as desired. The groove may also have different direction of turning in different parts of the hose, or different cross-sectional shape in different parts of the hose. This results in many possibilities of variation.
Preferably the hose has one or more expansion portions, which are distributed along the circumference of the hose casing, for satisfactory distribution of the pressure and/or shock equalisation in each individual case.
The invention also relates to a method for manufacturing a hose, according to the invention, in which the hose material is extruded. In addition to the hose material and together with this, a form material is extruded which is adapted to be a preform for the hose material for the desired configuration of expansion portions and wall portions. This preform serves to facilitate the process of extrusion. When the hose material, before blowing, has a relatively small diameter, there is a great risk that parts of the hose adhere to each other. This concerns in particular the expansion portions whose dimensions in the non-blown state are relatively small. A supporting form with expansion and wall portions is formed of the form material during extrusion and prevents problems in the forming of the hose material.
The form material is suitably arranged along the outer circumference of the hose material, which gives practical advantages in the method.
Preferably the form material is accumulated in the portions of the hose material which are intended to form expansion portions. These portions usually constitute formed portions such as grooves. The bulging shape which is necessary for the hose is produced by means of an elevated portion in the form material, thus a thicker portion of form material.
The form material can advantageously consist of an elastic material which extends along the circumference of the hose material. The form material of the completed hose will then be arranged along the circumference of the hose material and provides a smooth outer face for the hose. The elasticity of the material serves to make it possible for the expansion portions still to assume an unexpanded and an expanded state. A smooth outer face round the hose is advantageous since it is easier to keep clean than a hose with exposed expansion portions. The hose is then along its circumference provided with an elastic material.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.